It has been heretofore known to serially link a number of independent devices or units in a manner that will permit the units to evoke a message depending up on the order in which they are linked. Typically, one of the units is a command or base unit. The rest of the units are peripheral units or subunits. It may be further desired to transmit to the base unit the identity of each subunit as well as the order in which the subunits are connected.
An example of such a serially linked system is a child's educational toy in the form of a train whose cars represent letters of the alphabet and can be interchanged to form words. The base unit, or engine, collects data from each car and emits a response appropriate to whether a word has been correctly spelled.
Another example is a computer system coupled to a group of serially linked peripheral devices, such as data collection devices, printers or storage devices. The computer system collects data from each device to determine which devices are present and in what order.
Various schemes have been heretofore developed which use a number of data lines to allow the base unit and the subunits, coupled in a serial chain or train, to communicate with the base unit. Additionally, a number of power lines can be used to provide power from the base unit to the subunits. Typically, each subunit is equipped with two connectors, and the base unit with one connector. These connectors couple the data and power lines from the base unit to the first subunit, and from each subunit to the next subunit.
A problem with this coupling scheme is that the combined number of data and power lines is often more than standard, off-the-shelf connectors can accommodate. Therefore, custom made connectors must be used in place of off-the-shelf connectors. A need thus exists for a data and power connection scheme that minimizes the number of lines.